提出了一种具有高频率、宽频带和低电压特点的矩形同轴曲折波导慢波结构，所提出的矩形同轴曲折波导工作于过模状态，工作频率较高，同时具有不错的传输特性。设计了一种宽带的双脊加载的波导-同轴转换器，其带宽可以覆盖矩形同轴曲折波导行波管的整个工作频带。所设计的矩形同轴曲折波导行波管工作电压和电流分别为3230 V和150 mA，慢波结构长度为32 mm，PIC仿真结果表明，在76～110 GHz频率范围内，其输出功率超过13.7 W，在108GHz频点，输出功率达到最大值，约为27.4 W，对应的射频效率为 5.65%。

To develop high frequency, broad bandwidth and low voltage traveling wave tube (TWT), the folded rectangular coaxial waveguide slow wave structure (FRCW-SWS) is proposed in this paper. Operating at overmoded condition, the proposed FRCW-SWS has relatively high operating frequency and acceptable transmission characteristics. A double ridge-loaded waveguide-to-coaxial-waveguide converter is designed and applied as the input/output coupler to incorporate the broadband characteristics of the FRCW-SWS. The hot performance of this overmoded FRCW-TWT at W-band is investigated using particle-in-cell (PIC) simulation. The simulation results indicate that the output power can be over 13.7 W in the frequency range of 76～110 GHz, when the length of the SWS, the beam voltage and beam current are 32 mm, 3230 V and 150mA, respectively. The maximal output power is about 27.4 W at the frequency of 108 GHz, corresponding to the RF efficiency of 5.65%.